It is Dave. Dave is just a sailor. He jumped shit with everyone else, as Hossan says in an email to Bellic. The body found in the Humboldt is that of the ship's Captain, also said by Hossan and the in-game radio. UPDATE: I stand corrected. Yes, Dave was the one who died in the Humboldt. Although I heard that they found the Captain in the river too, with heaps of alcohol in his system.--Dominic-079